Yes! i had a cracked carburetor boot, and extra air was leaking into the engine, causing the air/fuel mix to get all screwed up.
I also think it would start after sitting because it gave the carb time to leak gas into the motor wich "choked" it.
Unfortunately though, 2 days ago, I was doing a very aggressive sprint down a dirt road, and the bike lost power, and wouldn't start up again.
Took it home, and blamo!
So now I got to get a new piston, and probably split the cases to get the pieces of smoked piston out of the crankcase.
Unless anyone else has an idea????